The present invention concerns dicarboxylic acid diamides, the amine component of which is dicyclohexylamine. Said dicarboxylic acid diamides form lithium complexes which are soluble in lipophilic solvents. The dicarboxylic acid diamides have a high selectivity for lithium ions compared with their selectivity for other alkali metal ions and alkaline earth metal ions. The dicarboxylic acid diamides can be used as ion selective component of ion selective membranes for the determination of the concentration of lithium ions and furthermore as component of test means, for instance test strips for the determination of lithium ions in liquid media.
A further object of the invention are processes for the preparation of the new dicarboxylic acid diamides.